In perpendicular magnetic recording (PMR), a trailing shield, as well as side shields and a leading shield, are used in order to produce a greater on-track field gradient thereby achieving a better signal to noise ratio together with high linear density and lower fringing fields for this high track density.
FIG. 1 is a cross-sectional view of a magnetic write head of the prior art. As can be seen, interface 11 is present between first trailing shield 12 and second trailing shield 13. Also shown in the figure are leading shield 14, main pole 15, top yoke 16, and field coils 17.
FIGS. 2a-2c show air-bearing surface (ABS) views of FIG. 1 for three of several different arrangements of the shields that are possible. In all three figures unlabeled diagonal arrows indicate wherever there is a physical interface between two regions (such as 11 in FIG. 1) while the presence of broken lines separating two regions having different functions (e.g. between side shields 21 and first trailing shield 12 in FIG. 2a. Note the presence of physical interface 11 in all three figures. Although no corresponding figure has been provided, write heads that are otherwise similar to those shown in FIG. 2, but having no side shields, are also sometimes used.
Unfortunately, the various shields shown in FIGS. 1 and 2 often cause unintended data erasure that is largely dependent on the geometry of the shields. The present invention has determined the source of the unintended erasure and discloses how this problem may be overcome.
A routine search of the prior art was performed with the following representative reference of interest being found:
In U.S. Pat. No. 7,477,481, Guthrie et al. show only one trailing shield. Note that no references teaching first and second trailing shields nor of the use of a sacrificial material in forming the trailing shield, were found.